『Abstract
　Nitrogen released to air and water are low in most of Canada, but in southern areas with rapid development there are telltale signs of the problems from releases to air and water that are described elsewhere in this volume. These include higher nitrogen in water and releases to the atmosphere from urban areas, industry and agriculture. As a result, in parts of Ontario and Quebec underlain by Precambrian geology, nitrogen deposition is near the critical loads found for geologically similar areas of Europe. In particular, combined inputs of sulphuric and nitric acids are causing base cation depletion in forest soils and keeping some lakes at pH values too low to allow the recovery of biological communities. In southern Ontario, Alberta and British Columbia, rapidly expanding human populations, industry and agriculture are causing high concentrations of nitrate in surface and groundwaters. At present, there is little sign of estuarine eutrophication in Canada, but it appears to be imminent on the Pacific coast, as the result of expanding human populations and intensifying agriculture in the lower Fraser Valley and Puget Sound. Steps should be taken now to prevent the widespread problems caused by nitrogen pollution that have occurred in Europe, the USA, and other populous and industrialized regions.

Keywords: Acid rain; Agriculture; Eutrophication; Water pollution』

Introduction
Canada-wide trends in airborne emissions of nitrogen
Atmospheric deposition of nitrogen and its impact on ecosystems
　Eastern Canada
Impact of high nitrogen deposition on ecosystems
　Western Canada
　Increasing humans, livestock and commercial fertilizer as sources of atmospheric nitrogen
　The Athabasca Oil Sands
Agriculture and urbanization as direst sources of nitrogen to water
Eutrophication of freshwaters and marine ecosystems
Summary
Acknowledgements
References